nasopharyngeal microbiota
Following DNA extraction, the hypervariable V3-V4 region of the 16S rRNA gene was amplified by polymerase chain reaction using forward primer 338F and reverse primer 806R. PCR amplification products were purified by Agencourt AMPure XP magnetic beads and dissolved in elution buffer, and the sizes and concentrations were measured using an Agilent 2109 Bioanalyzer. Qualified libraries were sequenced according to insert size on an Illumina MiSeq instrument.